Typescript conversion: app/component/FileIndex

[lsparlin]

Linked Issue

• closes Convert FileIndex.jsx to TypeScript #684

Description

Migrate src/component/FileIndex.js to typescript.

export FileListItem from PostList for type-checking

Methodology

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[danieltott]

Thank you @lsparlin !

I have a couple changes here.

The as FileListItem[] is perfect for the second reduce parameter, but it's actually hiding some issues when using it in the body (lines 40, 53, and 72). We should assign types to those returned variables normally so that typescript can do type checking - when you use as, we're basically promising we're matching the type and telling typescript to not check them at all.

Once you do this, you'll see that we need to adjust the type definitions - since children can be null.

Let me know if you have any questions about this!

[danieltott]

Thanks @lsparlin!!

Just as a note - I remembered this just now while reviewing, for reducers we can actually send the type of the initial value / accumulator param as a generic to reduce like this: files.reduce<FileListItem[]> - that way we don't need to use as at all! I made this change, I just wanted to let you know about it 👍🏼